Hardfacing of Nimonic 75 using 2 kW continuouswave CO₂ laser

Abstract

The ability of a 2kW continuous-wave CO₂ laser locally to melt a substrate allows controlled deposition of surface-hardening alloys. In the present study single tracks of Stellite 12 were applied to a substrate of Nimonic 75. This was achieved by using the defocused laser beam to melt a layer of Stellite 12 powder resting on the substrate. The main process parameters controlling the deposition were identified and an operating chart produced. Track widths in the range 1–4mm with thicknesses of 0·75–1·25mm were obtained using this technique. The maximum rate at which these tracks can be produced is afunction of laser power, laser beam diameter, and the powder thickness. At 2kW a 2mm wide track 1mm thick can be produced at a rate of 22 mms⁻¹. The deposition of coatings over closely defined areas is demonstrated and the advantages, disadvantages, and possiblefuture developments of the process are examined.